A trait for symfony to simplify adding the EntityManager to a class

HasEntityManager.php

<?php
declare(strict_types=1);

namespace App\Traits;

use Doctrine\ORM\EntityManagerInterface;
use Doctrine\Persistence\ObjectRepository;

trait HasEntityManager
{
    private ?EntityManagerInterface $entityManager = null;

    /**
     * @required
     */
    public function setEntityManger(EntityManagerInterface $entityManager) : static
    {
        $this->entityManager = $entityManager;
        return $this;
    }

    public function getEntityManager() : EntityManagerInterface
    {
        return $this->entityManager;
    }

    private function emPersist(object $object) : static
    {
        $this->getEntityManager()->persist($object);
        return $this;
    }

    private function emFlush() : static
    {
        $this->getEntityManager()->flush();
        return $this;
    }

    private function emPersistAndFlush(object $object) : static
    {
        return $this->emPersist($object)
            ->emFlush();
    }

    private function emGetRepository(string $className) : ObjectRepository
    {
        return $this->getEntityManager()->getRepository($className);
    }

    private function emFindOneBy(string $className, array $criteria) : ?object
    {
        return $this->emGetRepository($className)->findOneBy($criteria);
    }

    private function emFindOneByOrThrow(string $className, array $criteria, string $throwMessage = 'Unable to find results') : object
    {
        $res = $this->emFindOneBy($className, $criteria);

        if ($res === null) {
            throw new \RuntimeException($throwMessage);
        }

        return $res;
    }

    private function emFindBy(string $className, array $criteria) : array
    {
        return $this->emGetRepository($className)->findBy($criteria);
    }
}